This invention relates to an improved apparatus for applying an electrostatic charge to fibrous structures and depositing them on a moving receiver to form a nonwoven sheet. More particularly, it relates to an improvement in the aerodynamic shield disclosed in U.S. Pat. No. 3,860,369.
Associated with the flash spinning of fibrous structures is the need to impart a higher electrical charge to the structure to improve uniformity of the nonwoven sheet structure deposited on the receiver. The higher the charge applied the more uniform is the resultant nonwoven sheet. A consequence of increasing the level of charge applied to the fibrous structure is an increase in charge build up on the aerodynamic shield members which have a resistance of about 10.sup.17 ohms/sq. When a sufficient surface charge is built up on the aerodynamic shield members, arcing on the surface of and between shield members occurs which in turn discharges a portion of the fibrous structure as it passes between the shield members to the receiver leading to web collapse and sheet imperfections.
Previous solutions to arcing between aerodynamic shield members involved reducing the amount of charge imparted to the fibrous structure which consequently resulted in poorer sheet uniformity.